Recording elements or media typically comprise a substrate or a support material optionally having on at least one surface thereof an image-forming layer. The elements include those intended for reflection viewing, which usually have an opaque support, and those intended for viewing by transmitted light, which usually have a transparent support.
While a wide variety of different types of image-recording elements have been proposed, there are many unsolved problems in the art and many deficiencies in the known products which have severely limited their commercial usefulness. These deficiencies vary with the type of image recording element.
The requirements for an image-recording medium or element for ink-jet recording are very demanding. For example, the recording element should be capable of absorbing or receiving large amounts of ink applied to the image-forming surface of the element as rapidly as possible in order to produce recorded images having high optical density and good color gamut.
One example of an opaque image-recording element is described in U.S. Pat. No. 5,326,391. It consists of a layer of a microporous material which comprises a matrix consisting essentially of a substantially water-insoluble thermoplastic organic polymer, such as a linear ultra-high molecular weight polyethylene, a large proportion of finely divided water-insoluble filler of which at least 50 percent by weight is siliceous and interconnecting pores. The porous nature of the image-recording element disclosed in U.S. Pat. No. 5,326,391 allows inks to penetrate the surface of the element to produce text and/or graphic images. However, the cost of producing these elements is relatively high. Also, the image density has been found to be of poor quality, that is, the images have low optical densities and poor color gamut.
U.S. Pat. No. 5,605,750 has already addressed the latter shortcomings of image density and color gamut via the application of an upper image-forming layer. This upper image forming layer is a porous, pseudo-boehmite having average pore radius of from 10 to 80 Å. However, the high manufacturing cost of the article to form the absorbent layer is not solved in U.S. Pat. No. 5,605,750. This is due to the requirements for the porous substrate as described in U.S. Pat. No. 5,326,391.
U.S. Pat. No. 6,379,780 describes a porous substrate that may be manufactured at low cost. Further, U.S. Pat. No. 6,481,843 describes an ink jet recording element comprising the porous substrate of U.S. Pat. No. 6,379,780 including a porous image receiving layer with interconnecting voids resulting in an image recording element manufacturable at low cost and having high image quality and durability. The top porous layer of the substrate described in U.S. Pat. No. 6,379,780 and U.S. Pat. No. 6,481,843 tears apart when attempting to manufacture it as a single layered substrate. To function adequately as a support, the substrate must comprise multiple layers with a subsequent supporting layer which prevents the substrate from tearing, enabling manufacturability. This results in the need to co-extrude the substrate when manufacturing so as to include the supporting layer under the top porous layer.
It is desirable to extrude only a single layer when producing a substrate for an ink jet recording element that is porous and ink-permeable. This would enable most manufacturing machines capable of manufacturing polyester films to produce such a substrate without the need of co-extrusion capability. This is important as a relatively small number of polyester machines are capable of co-extruding. Thus, it can be seen that a need still exists in the art for the provision of an opaque image-recording element suitable for use in an inkjet printer, which is capable of recording images (including color images) having fast dry times, high optical densities and good color gamut, capable of being manufactured at a relatively low cost, and capable of being produced on existing polyester film manufacturing machines without the need of co-extrusion capability.
The use of immiscible polymer particles, such as olefins, in the polyester matrix as a void initiator has been described in U.S. Pat. No. 4,187,113. This means of voiding is very robust and results in a low cost means to void polyester. The immiscible polymer may be added simultaneously with manufacturing the substrate. Such voided layers have been shown to be manufacturable as a single layered media. However, the use of such voided polyester may not achieve open cell voids which typically enable absorbency for an ink jet imaging media. Also, the use of such voided polyester matrix layers in an ink jet imaging media has been shown to be deficient in terms of image quality. Thus the use of immiscible polymer particles does not by itself offer a solution to the problems observed with microbeads as described above.
The problem to be solved by the present invention is to formulate an opaque ink jet imaging media with a single layer substrate suitable for use in an ink-jet printer, which is capable of recording images (including color images) having fast dry times, high optical densities and good color gamut, capable of being manufactured at a relatively low cost, and capable of being produced on existing polyester film manufacturing machines without the need of co-extrusion capability.